/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.test.checkpointing.utils;

import org.apache.flink.api.common.accumulators.IntCounter;
import org.apache.flink.api.common.state.ListState;
import org.apache.flink.api.common.state.ListStateDescriptor;
import org.apache.flink.api.common.typeutils.base.StringSerializer;
import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.configuration.Configuration;
import org.apache.flink.runtime.state.FunctionInitializationContext;
import org.apache.flink.runtime.state.FunctionSnapshotContext;
import org.apache.flink.streaming.api.checkpoint.CheckpointedFunction;
import org.apache.flink.streaming.api.functions.sink.RichSinkFunction;
import org.apache.flink.streaming.api.functions.source.RichParallelSourceFunction;
import org.apache.flink.streaming.api.functions.source.RichSourceFunction;
import org.apache.flink.streaming.api.functions.source.SourceFunction;
import org.apache.flink.streaming.api.watermark.Watermark;

import static org.hamcrest.Matchers.containsInAnyOrder;
import static org.junit.Assert.assertThat;

/**
 * A utility class containing common functions/classes used by multiple migration tests.
 */
public class MigrationTestUtils {

	/**
	 * A non-parallel source with list state used for testing.
	 */
	public static class CheckpointingNonParallelSourceWithListState
			implements SourceFunction<Tuple2<Long, Long>>, CheckpointedFunction {

		static final ListStateDescriptor<String> STATE_DESCRIPTOR =
				new ListStateDescriptor<>("source-state", StringSerializer.INSTANCE);

		static final String CHECKPOINTED_STRING = "Here be dragons!";
		static final String CHECKPOINTED_STRING_1 = "Here be more dragons!";
		static final String CHECKPOINTED_STRING_2 = "Here be yet more dragons!";
		static final String CHECKPOINTED_STRING_3 = "Here be the mostest dragons!";

		private static final long serialVersionUID = 1L;

		private volatile boolean isRunning = true;

		private final int numElements;

		private transient ListState<String> unionListState;

		public CheckpointingNonParallelSourceWithListState(int numElements) {
			this.numElements = numElements;
		}

		@Override
		public void snapshotState(FunctionSnapshotContext context) throws Exception {
			unionListState.clear();
			unionListState.add(CHECKPOINTED_STRING);
			unionListState.add(CHECKPOINTED_STRING_1);
			unionListState.add(CHECKPOINTED_STRING_2);
			unionListState.add(CHECKPOINTED_STRING_3);
		}

		@Override
		public void initializeState(FunctionInitializationContext context) throws Exception {
			unionListState = context.getOperatorStateStore().getListState(
					STATE_DESCRIPTOR);
		}

		@Override
		public void run(SourceContext<Tuple2<Long, Long>> ctx) throws Exception {

			ctx.emitWatermark(new Watermark(0));

			synchronized (ctx.getCheckpointLock()) {
				for (long i = 0; i < numElements; i++) {
					ctx.collect(new Tuple2<>(i, i));
				}
			}

			// don't emit a final watermark so that we don't trigger the registered event-time
			// timers
			while (isRunning) {
				Thread.sleep(20);
			}
		}

		@Override
		public void cancel() {
			isRunning = false;
		}
	}

	/**
	 * A non-parallel source with union state used to verify the restored state of
	 * {@link CheckpointingNonParallelSourceWithListState}.
	 */
	public static class CheckingNonParallelSourceWithListState
			extends RichSourceFunction<Tuple2<Long, Long>> implements CheckpointedFunction {

		private static final long serialVersionUID = 1L;

		static final String SUCCESSFUL_RESTORE_CHECK_ACCUMULATOR = CheckingNonParallelSourceWithListState.class + "_RESTORE_CHECK";

		private volatile boolean isRunning = true;

		private final int numElements;

		public CheckingNonParallelSourceWithListState(int numElements) {
			this.numElements = numElements;
		}

		@Override
		public void snapshotState(FunctionSnapshotContext context) throws Exception {

		}

		@Override
		public void initializeState(FunctionInitializationContext context) throws Exception {
			ListState<String> unionListState = context.getOperatorStateStore().getListState(
					CheckpointingNonParallelSourceWithListState.STATE_DESCRIPTOR);

			if (context.isRestored()) {
				assertThat(unionListState.get(),
						containsInAnyOrder(
								CheckpointingNonParallelSourceWithListState.CHECKPOINTED_STRING,
								CheckpointingNonParallelSourceWithListState.CHECKPOINTED_STRING_1,
								CheckpointingNonParallelSourceWithListState.CHECKPOINTED_STRING_2,
								CheckpointingNonParallelSourceWithListState.CHECKPOINTED_STRING_3));

				getRuntimeContext().addAccumulator(SUCCESSFUL_RESTORE_CHECK_ACCUMULATOR, new IntCounter());
				getRuntimeContext().getAccumulator(SUCCESSFUL_RESTORE_CHECK_ACCUMULATOR).add(1);
			} else {
				throw new RuntimeException(
						"This source should always be restored because it's only used when restoring from a savepoint.");
			}
		}

		@Override
		public void run(SourceContext<Tuple2<Long, Long>> ctx) throws Exception {

			// immediately trigger any set timers
			ctx.emitWatermark(new Watermark(1000));

			synchronized (ctx.getCheckpointLock()) {
				for (long i = 0; i < numElements; i++) {
					ctx.collect(new Tuple2<>(i, i));
				}
			}

			while (isRunning) {
				Thread.sleep(20);
			}
		}

		@Override
		public void cancel() {
			isRunning = false;
		}
	}

	/**
	 * A parallel source with union state used for testing.
	 */
	public static class CheckpointingParallelSourceWithUnionListState
			extends RichSourceFunction<Tuple2<Long, Long>> implements CheckpointedFunction {

		static final ListStateDescriptor<String> STATE_DESCRIPTOR =
				new ListStateDescriptor<>("source-state", StringSerializer.INSTANCE);

		static final String[] CHECKPOINTED_STRINGS = {
				"Here be dragons!",
				"Here be more dragons!",
				"Here be yet more dragons!",
				"Here be the mostest dragons!" };

		private static final long serialVersionUID = 1L;

		private volatile boolean isRunning = true;

		private final int numElements;

		private transient ListState<String> unionListState;

		public CheckpointingParallelSourceWithUnionListState(int numElements) {
			this.numElements = numElements;
		}

		@Override
		public void snapshotState(FunctionSnapshotContext context) throws Exception {
			unionListState.clear();

			for (String s : CHECKPOINTED_STRINGS) {
				if (s.hashCode() % getRuntimeContext().getNumberOfParallelSubtasks() == getRuntimeContext().getIndexOfThisSubtask()) {
					unionListState.add(s);
				}
			}
		}

		@Override
		public void initializeState(FunctionInitializationContext context) throws Exception {
			unionListState = context.getOperatorStateStore().getUnionListState(
					STATE_DESCRIPTOR);
		}

		@Override
		public void run(SourceContext<Tuple2<Long, Long>> ctx) throws Exception {

			ctx.emitWatermark(new Watermark(0));

			synchronized (ctx.getCheckpointLock()) {
				for (long i = 0; i < numElements; i++) {
					if (i % getRuntimeContext().getNumberOfParallelSubtasks() == getRuntimeContext().getIndexOfThisSubtask()) {
						ctx.collect(new Tuple2<>(i, i));
					}
				}
			}

			// don't emit a final watermark so that we don't trigger the registered event-time
			// timers
			while (isRunning) {
				Thread.sleep(20);
			}
		}

		@Override
		public void cancel() {
			isRunning = false;
		}
	}

	/**
	 * A parallel source with union state used to verify the restored state of
	 * {@link CheckpointingParallelSourceWithUnionListState}.
	 */
	public static class CheckingParallelSourceWithUnionListState
			extends RichParallelSourceFunction<Tuple2<Long, Long>> implements CheckpointedFunction {

		private static final long serialVersionUID = 1L;

		static final String SUCCESSFUL_RESTORE_CHECK_ACCUMULATOR = CheckingParallelSourceWithUnionListState.class + "_RESTORE_CHECK";

		private volatile boolean isRunning = true;

		private final int numElements;

		public CheckingParallelSourceWithUnionListState(int numElements) {
			this.numElements = numElements;
		}

		@Override
		public void snapshotState(FunctionSnapshotContext context) throws Exception {

		}

		@Override
		public void initializeState(FunctionInitializationContext context) throws Exception {
			ListState<String> unionListState = context.getOperatorStateStore().getUnionListState(
					CheckpointingNonParallelSourceWithListState.STATE_DESCRIPTOR);

			if (context.isRestored()) {
				assertThat(unionListState.get(),
						containsInAnyOrder(CheckpointingParallelSourceWithUnionListState.CHECKPOINTED_STRINGS));

				getRuntimeContext().addAccumulator(SUCCESSFUL_RESTORE_CHECK_ACCUMULATOR, new IntCounter());
				getRuntimeContext().getAccumulator(SUCCESSFUL_RESTORE_CHECK_ACCUMULATOR).add(1);
			} else {
				throw new RuntimeException(
						"This source should always be restored because it's only used when restoring from a savepoint.");
			}
		}

		@Override
		public void run(SourceContext<Tuple2<Long, Long>> ctx) throws Exception {

			// immediately trigger any set timers
			ctx.emitWatermark(new Watermark(1000));

			synchronized (ctx.getCheckpointLock()) {
				for (long i = 0; i < numElements; i++) {
					if (i % getRuntimeContext().getNumberOfParallelSubtasks() == getRuntimeContext().getIndexOfThisSubtask()) {
						ctx.collect(new Tuple2<>(i, i));
					}
				}
			}

			while (isRunning) {
				Thread.sleep(20);
			}
		}

		@Override
		public void cancel() {
			isRunning = false;
		}
	}

	/**
	 * A sink which counts the elements it sees in an accumulator.
	 */
	public static class AccumulatorCountingSink<T> extends RichSinkFunction<T> {
		private static final long serialVersionUID = 1L;

		public static final String NUM_ELEMENTS_ACCUMULATOR = AccumulatorCountingSink.class + "_NUM_ELEMENTS";

		int count = 0;

		@Override
		public void open(Configuration parameters) throws Exception {
			super.open(parameters);

			getRuntimeContext().addAccumulator(NUM_ELEMENTS_ACCUMULATOR, new IntCounter());
		}

		@Override
		public void invoke(T value, Context context) throws Exception {
			count++;
			getRuntimeContext().getAccumulator(NUM_ELEMENTS_ACCUMULATOR).add(1);
		}
	}
}
